In an electro-optic device such as a liquid crystal display device or an organic EL (electroluminescence) display device, pixel switching is performed using a thin film circuit composed of a thin film transistor as a semiconductor element. In conventional thin film transistors, active regions such as channel forming regions are formed with amorphous silicon films. Also, thin film transistors whose active regions are formed with polycrystalline silicon films have been in practical use. By using polycrystalline silicon films, electrical characteristics such as mobility are improved in comparison with using amorphous silicon films, thus improving performance of thin film transistors.
Further, in order to further improve performance of thin film transistors, a technology of forming a semiconductor film with large crystal grains to prevent grain boundaries from entering the channel regions of the thin film transistors is under review. For example, proposed is a technology in which a semiconductor film is crystallized using a microscopic opening, provided to a substrate, as a starting point of crystal growth to form large sized silicon crystal grains. Such a technology is described in, for example, Japanese unexamined patent publication No. 11-87243, “Single Crystal Thin Film Transistors,” IBM TECHNICAL DISCLOSURE BULLETIN August 1993 pp. 257–258, and “Advanced Excimer-Laser Crystallization Techniques of Si Thin-Film For Location Control of Large Grain on Glass,” R. Ishihara et al., proc. SPIE 2001, vol. 4295 pp. 14–23. By forming thin film transistors using a silicon film having large sized grains formed by the technology, the grain boundaries can be prevented from entering the single thin film transistor forming area (particularly the channel forming area). Thus, thin film transistors superior in electronic characteristics such as mobility can be realized.